[Tex/LaTex] How to automatically dot fill line in Math mode

align

I need to dot fill line in math mode even in aligned environment. I'm using \makebox[width]{\dotfill} but for presentation accommodations I want that dots reach the end of line.
I know that there exist linegoal to compute the missing space but I can't find how to apply this in math mode. Is there anyway to get the missing space.

\documentclass[a4paper,12pt]{article}
\usepackage{multido}
\usepackage{amsmath}
\usepackage{lipsum}

\begin{document}
\lipsum[8]\parskip 1\baselineskip
\noindent 
$f(x)=\frac{1}{\sqrt{x^7}}\Rightarrow 
                  \begin{aligned}[t]
                    f'(x) & =\makebox[.6\linewidth]{\dotfill} \\[1.5\baselineskip] 
                          & =\makebox[.6\linewidth]{\dotfill} 
                  \end{aligned}$
\end{document}

Best Answer

Since it seems you're interested in using the full width of the text block, you might as well use another mechanism to set the equation. Below I've used tabularx as it allows for a p-type column that stretches as far needed to fill (say) \textwidth:

\documentclass{article}
\usepackage{tabularx}
\usepackage{lipsum}

\begin{document}

\lipsum[8]

\vspace{\abovedisplayskip}

\noindent
\begin{tabularx}{\textwidth}{@{}l@{~}X@{}}
  $f(x) = \frac{1}{\sqrt{x^7}} \Rightarrow$
    & \dotfill \\[1.5\normalbaselineskip]
    & \dotfill
\end{tabularx}

\vspace{\belowdisplayskip}

\noindent
\lipsum[9]

\end{document}

Related Solutions

[Tex/LaTex] How to write multi line equations with alignment in inline math mode

In such cases you could simply use the aligned environment within inline math instead of align*:

\documentclass{article}
\usepackage{amsmath}
\begin{document}
text
$\begin{aligned}
x+y&=z\\
u+v&=w
\end{aligned}$
more text
\end{document}

Output:

alt text

[Tex/LaTex] Tabbing for math mode

As per Math indentation environment, the alignat provides multiple rl align pairs. Since your second alignment is intended to be l aligned, you need to use a double &&. The first & skips over the r aligned column of the rl align pair:

enter image description here

Notes:

The align environment also provides multiple rl alignment pairs. However, the alignat does not insert additional space that the align environment does between the rl alignment pairs. So, for cases where a separation is required between the alignment points with the alignat environment those would need to be inserted manually.
An alternative is to use the array environment. But one does need to be careful to remove inter column spacing using @{}, and to ensure that the relational or binary operators have the correct spacing by using {} to make TeX think that there is an element on the other side of the operator. This produces results identical to the above.

Code:

\documentclass{article}
\usepackage{amsmath}
\begin{document}

\begin{alignat*}{3}
S_4^{t} &= \{&&\langle rdi, r12, rax' \rangle \mid \langle rdi, r12, rax \rangle \in S_4~\wedge \\
        &    &&rax' = \{ rax \mid rax > 0 \} \}
\end{alignat*}

\[\begin{array}{l@{}l@{}l}
S_4^{t} &{}= \{&\langle rdi, r12, rax' \rangle \mid \langle rdi, r12, rax \rangle \in S_4~\wedge \\
        &      &rax' = \{ rax \mid rax > 0 \} \} \\
\end{array}\]
\end{document}